This invention relates to load binders and more particularly to the so-called over center, lever operated type of load binder. Such devices are used to tension chains or cables or the like such as used, for example, in tying down and securing large loads on flat bed trucks. Prior art examples of typical load binders are disclosed in U.S. Pat. Nos. 396,714; 1,518,769; 1,972,346; 2,539,997; 3,826,469; 4,122,587 and 4,422,218. Load binding devices are typically operated by manual pivoting of a handle which acts as a lever to provide the operator with a mechanical advantage when drawing the ends of the binder toward one another. The tension is maintained by moving the lever into an over center locked position behind a lever pivot point.
The load binding device is typically released by manual rotation of the lever in the direction opposite tensioning. A serious problem can be encountered by operators when releasing over center load binders of the prior art, because when the lever passes from an over center locked position, through a dead center position the tension on the chain (or cable) exerts a sudden increased force which can cause the handle to "fly back". In many cases, particularly when the bound load has shifted during transit, the tension on the chain may be so substantially increased by the shifting of the load that the "fly back" problem is further exacerbated.
Thus, the operator may be exposed to the danger of a flaying lever over which he may lose control. Furthermore, since it is not unknown for an operator to inappropriately use a section of pipe to extend the length of the lever arm of the load binder to achieve increased leverage for releasing a bound load that has shifted into extremely high tension arrangement, the danger of a flaying lever becomes multiplied.
U.S. Pat. No. 4,366,607 discloses an over center type load binder which provides a degree of lost motion such that the crank mechanism can overrun the operating lever on passing the dead center position. Such device can be effective in avoiding the fly back problem, but unless the handle is removed or tied down, it can swing dangerously about as the vehicle carrying the load bumps along a typical roadway and may, under some conditions, jar the crank mechanism to accidental release.
It is an object of the present invention to provide an improved load binder of the over center type which will enable the operator to provide leveraged tensioning forces on a chain system or the like and lock the binder in tensioned condition. Another object is to provide a load binder having resistance to handle swing during roadway travel and improved ease of tension release with decreased danger of handle fly back problems. Still another object is to provide a load binder embodying the features of the invention which is of simple construction, inexpensively manufactured, rugged and maintenance free.